These developments - a massive transfer of land by way of inheritance and purchase, an unprecedented rise in the profitability of land and increasing intermarriage between Celtic and English dynasties - helped to consolidate a new unitary ruling class in place of the more separate and specific landed establishments that had characterised England, Scotland, Wales and Ireland in the Tudor and Stuart eras.

Jacobitism involved much more than a debate about the merits of a particular dynasty. Men and women were well aware that its success was almost certain to involved them in civil war. And the more politically educated knew that the Stuart Pretender was a pawn in a worldwide struggle for commercial and imperial primacy between Britain and France.

Human beings are many-layered creatures, and do not succumb to the hegemony of others as easily as historians and politicians sometimes imply. Those Welsh, Scottish and Anglo-Irish individuals who became part of the British Establishment in this period did not in the main sell out in the sense of becoming Anglicised look-alikes. Instead, they became British in a new and intensely profitable fashion, while remaining in their own minds and behavior Welsh, or Scottish, or Irish aswell.

These developments - a massive transfer of land by way of inheritance and purchase, an unprecedented rise in the profitability of land and increasing intermarriage between Celtic and English dynasties - helped to consolidate a new unitary ruling class in place of the more separate and specific landed establishments that had characterised England, Scotland, Wales and Ireland in the Tudor and Stuart eras.

At one level Great Britain at the beginning of the 18th century was like the Christian doctrine of the Trinity, both three and one, and altogether something of a mystery.

Recognising that an ostentatious cult of heroism and state service served an important propaganda function for the British elite does not mean, of course, that we should dismiss it as artificial or insincere. All aristocracies have a strong military tradition, and for many British patricians the protracted warfare of the period was a godsend. It gave them a job, and, more important, a purpose, an opportunity to carry out what they had been trained to do since childhood: ride horses, fire guns, exercise their undoubted physical courage and tell other people what to do.

Virtually every war fought since the Act of Union had gone badly at some stage, but before 1783 none had ended in defeat. Nor would any major war in which Britain was involved after this date end in defeat. Those who are curious about this country's peculiar social and political stability probably need look no further than this for essential cause.